Answers to questions 15,19,20,21 &25

The answer to your question is below

Step-by-step explanation:

15. x² = 144

    x = √144

   x = ± 12

19. 9x² = 4

      x² = 4/9

      x = √4/9

    x = ± 2/3

20.

      25y² = -16

          y² = -16/25

          y = √-16/25

          y = ± 4/5 i

21. 16y² = 25

        y² = 25/16

        y = √25/16

        y = ±5/4

25.

       81 - 9x² = 0

       81 = 9x²

       81/9 = x²

         9 = x²

       √9 = x

        x = ± 3

a

explanation:

distance covered by pamela in 9 l of fuel = 99km

let us apply unitary method here.

distance covered by pamela in 1 l of fuel =99/9 =11 km

now let us find distance covered by pamela if she has 12 l of fuel.

distance covered in 12 l = distance covered in 1 l of fuel * 12

we know that distance covered by here in 1 l is 11 km.

so distance covered in 12 l of fuel = 11*12 = 132 km.